As the requirement for the wireless access rate is becoming higher and higher, the WLAN that can provide a higher wireless access rate within a smaller area has seen in fast development. Nowadays, there are many available technologies for WLAN, one widely applied technical standard of which is IEEE 802.11b that uses the frequency band of 2.4 GHz; another alternative that uses the same frequency band is the Bluetooth. All other new technologies, such as IEEE 802.11a and ETSI BRAN Hiperlan2, use the frequency band of 5 GHz.
Although there are many different kinds of radio access technologies, most WLANs are used to bear IP (Internet Protocol) data packets. In a wireless IP network, the WLAN access technology specific is usually transparent to the upper layer, e.g. IP layer or upper. All these IP networks are of the similar basic architecture which implements the wireless access of a user via the Access Point (AP) and builds an IP transmission network through the connection of the network control and connection devices.
Along with the springing up and development of the WLAN, how to implement the interworking between the WLAN and various mobile communication networks, such as GSM, CDMA (Code-Division Multiple Access) system, WCDMA (Wideband Code Division Multiple Access) system, TD-SCDMA (Time Division-Synchronize Code Division Multiple Access) system and CDMA2000 system, has become one of the highlights of current research. In the scope of 3rd Generation Partnership Project (3GPP) standard organization, simplified network architecture for interworking between a WLAN system and a 3GPP system is shown in FIG. 1. A user terminal can communicate with not only the Internet and Intranet but also the packet domain network of the 3GPP network via WLAN access networks. It is obvious that, as a wireless access technology that provides IP bearer, the WLAN can be interconnected with many other networks.
Generally, while the WLAN connects with other networks, the authentication, authorization and accounting operation for the connection are controlled by an appropriate application server, for instance, the AAA (Authentication, Authorization and Accounting) server in a 3GPP system; and the subscriber information is managed by an information storage unit, for example, the HSS (Home Subscriber Server) or the HLR (Home Location Register) in the 3GPP system. Therefore, when the authentication, authorization and accounting processes is performed, the corresponding application server will request the user profile from the information storage unit, and store it temporarily in itself. The application server will not release the information stored until the service is terminated, wherein the so-called release refers to the step that the application server deletes the relevant data of the user who is not access the service any more. In specific implementation, the data can be deleted immediately after the user is offline, or be kept for a certain period of time before being deleted so that when the user logs in once again, the application server can use the stored data again without downloading it from the information storage unit. Once the subscriber information in the information storage unit is changed, the information storage unit will notify the corresponding application server to update the data.
In practice, there is no corresponding mechanism in the 3GPP standard supporting the attach process by which a WLAN user requests to access WLAN, i.e. the WLAN attach process. As a result, a WLAN user cannot know whether he/she has successfully accessed the WLAN, and whether he is able to use the services provided by the WLAN. In addition, the AAA server cannot determine whether the WLAN based services are available to the user. Similarly, there also is no corresponding mechanism in the 3GPP standard supporting the detach process by which a WLAN user stops using the services and is detached from the WLAN, i.e. the WLAN detach process. Consequently, the WLAN user cannot make sure whether he has successfully been detached from the WLAN, and furthermore, the AAA server is also unable to determine whether the user is still able to enjoy the WLAN based services.
In addition, in order to prevent unnecessary signaling delivery, it is necessary to synchronize the user information stored in the application server and that in the information storage unit. For instance, in existing specifications, when a user is attached or detached in a WLAN, the information about user connection can be updated only in the service control unit, i.e. the user information application server, such as the AAA server, without notification of the information storage unit for the user, such as the HLR/HSS. The direct consequence of this mechanism is that the information storage unit will not know the accurate status information of the user, which makes the user information stored in the information storage unit unreliable. It is also possible that even after the user's disconnection from a WLAN, the information storage unit continues to ask for the user information, such as the service connection status of the user and the user data, from the service control unit in subsequent processing, which results in unnecessary signaling burden and meaningless system resource occupation. When there is a large amount of such signaling, negative effects may be brought to the normal operations of the system.